... measure the time someone keeps a key pressed? (case 3006)

[Luigi Della Mea Rodríguez]

I've tried with "key release", but what I need to know is how long does the subject keep pressed the key, not the time he takes to react since the onset of the stimulus.
I am working at a reproduction task of time perception: subjects have to keep a key pressed the same duration they believe a previous sound lasted.
Can you help me? Thanks a lot!